This invention relates generally to the burying of utility cables and more specifically to an apparatus for simultaneously burying a plurality of such cables in a previously excavated trench in a spaced relationship to each other and for protectively surrounding those spaced apart, buried cables with sand.
During the past decade, emphasis has been placed on the underground rather than above ground location of utility lines associated with new commercial and residential subdivisions. Environmental and aesthetic considerations, as well as reduced line maintenance costs, have made underground emplacement of those lines a desirable alternative to their historical location on poles. Generally, it is desired to place a number of cables, including electrical, telephone, and television cables, in a common excavated trench approximately four feet in depth. The proper placement and protection of such cables has been of continuing concern to the power utility companies due to the extremely high cost of replacing or repairing cables that have been damaged during emplacement. As a result, these companies have been unwilling to entrust this operation to subcontractors, preferring instead to utilize their own crews. Telephone and cable television companies have followed similar practices, which, in the aggregate, have resulted in far less than optimum protection for the cables to be buried. Because of the involvement of several utility companies in attempting to place different types of cables in a common trench, the logistics of coordinating the efforts of several crews makes simultaneous emplacement of all the necessary cables nearly an impossibility. Thus, a trench may often remain open for several weeks to accommodate the cable emplacement schedules of the various utility companies involved. During this time period, the walls of the trench often collapse, debris is permitted to fall into the trench, and damage regularly occurs to previously placed cables during subsequent emplacement operations.
Since the various cables are typically placed in the trench manually by the different utility company crews, a good deal of undesirable variation results in cable placement and cable separation. This problem is compounded by the wide range of cable types and sizes that may be placed in a given trench. In addition, backfill operations are generally conducted in an uncontrolled manner that permits cable damage due to the presence of rocks, debris, and other undesirable material that inadvertently falls directly on top of or adjacent to some of the cables. This problem is particularly significant in the case where dirt removed from the trench is used as the backfill material. In an attempt to minimize damage to the emplaced cables, some companies have adopted the practice of using sand as the initial backfill material. However, due to a lack of effective control in disbursing the sand, more sand than is necessary is used, further increasing costs. Moreover, the inefficient sand disbursement processes employed introduces further delays in the cable emplacement operations.
In order to minimize damage to buried cables, the various utility companies often employ very skilled and conscientious personnel who could be more efficiently utilized in other positions. Because of the lack of control inherent in the manual methods of cable emplacement that have been widely practiced over the past several years, minor damage or lack of protection to emplaced cables has often gone undetected. As a result, utility companies are now experiencing an increase in the frequency of maintenance and repair operations performed on existing underground lines. A frequent cause of failure has been previously undetected cable damage occuring at the time of emplacement.
Accordingly, it is the principal object of this invention to provide an apparatus for controllably placing a plurality of cables in a single trench so as to maintain a predetermined spatial relationship between the cables.
A further object of this invention is to provide an apparatus for controllably introducing sand backfill material at the time of emplacement of a plurality of underground cables.
An additional object of this invention is to provide a cable burying apparatus having means for guiding a plurality of cables from their individual supply reels into a previously excavated trench in a manner that affords maximum protection against damage to the cables.
Additional and incidental objects of the present invention will become apparent from the attached specification and drawings.
These objects are accomplished in accordance with the illustrated preferred embodiment of the invention by providing a sanding sled that is positioned for being pulled by a tractor or other vehicle along a previously excavated trench. The sanding sled receives a plurality of cables to be buried from a reel supply vehicle that precedes the sanding sled-tractor combination. A cable guide boom assembly collects the individual cables as they are unspooled from supply reels and spatially positions them for later placement in the trench. The cables are guided through the sanding sled so as to exit the sanding sled in a predetermined spatial relationship to each other. A sand supply vehicle that moves in concert with the sanding sled controllably releases sand into a chamber portion of the sanding sled that serves to funnel the sand into the areas between the individual cables so that the desired spatial relationship between the cables is maintained.